Direct current motor

ABSTRACT

A direct-current motor comprises: a stator including a shell, a main magnetic pole, and an exciting coil; a rotator disposed inside the stator; a brush holder disposed at an end of the shell; first and second carbon brushes disposed on the brush holder and contacted with the rotator, respectively; a current-direction controller disposed on the brush holder and connected with the first and second carbon brushes and first and second ends of the exciting coil, respectively, to control a direction of a current supplied to the exciting coil; and a cover disposed at the end of the shell to enclose the brush holder. The motor is compact in structure, small in volume, and occupies a small mounting space, and the work load of sealing and insulating is reduced, thus reducing the cost and improving the manufacture efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a “continuation” application and claims benefit of the filing date of U.S. patent application Ser. No. 12/831307 filed on Jul. 7, 2010 and entitled “Direct Current Motor,” which, in turn, is based upon and claims priority to Chinese Patent Application 200910174206.5 filed on Sep. 23, 2009.

BACKGROUND OF INVENTION

1. Field of Invention

The invention relates to, in general, a motor and, in particular, a series-excited direct-current (DC) motor.

2. Description of Related Art

For a DC motor capable of rotating in forward and inverse directions, the rotating direction is changed by changing a direction of the current supplied to the exciting coil. Conventionally, the controller capable of changing the direction of the current supplied to the exciting coil is disposed outside the motor (for example, mounted on the outer surface of the motor shell) and usually includes four contactors so that the controller has a plurality of wires and connection points.

Therefore, the motors of the type commonly known n the related art have a large volume, are not compact in structure, and occupy a large mounting space. Moreover, the controller needs to be enclosed, and the wires and connection points thereof need to he sealed and insulated, respectively. These requirements increase the cost and reduce the operating efficiency of the motors.

Additionally, due to the large number of the wires and connection points, the work load of sealing and insulating the motor is large, the operation is complex, and the power consumption is increased. Further, because the controller is disposed outside the motor, the current-direction controller and wires and connection points thereof tend to be damaged, thus causing higher maintenance cost.

SUMMARY OF INVENTION

The invention overcomes problems existing in the related art in a direct-current motor comprising a stator including a shell, a main magnetic. pole, and an exciting coil. A rotator is disposed inside the stator, A brush holder is disposed at an end of the shell. First and second carbon brushes are disposed on the brush holder and contacted with the rotator, respectively. A current-direction controller is disposed on the brush holder and connected with the first and second carbon brushes and first and second ends of the exciting coil, respectively, to control a direction of a current supplied to the exciting coil, A over is disposed at the end of the shell to enclose the brush holder.

Accordingly, a DC motor is provided, in which a current-direction controller is disposed inside the motor so that wires and connection points may he decreased, the power consumption may be reduced, the operating efficiency may be improved, the current-direction controller and wires and connection points thereof are not easy to damage, the work load of sealing and insulating may he reduced, and the structure of the motor may be compact.

The motor according to the embodiment of the invention is compact in structure, small in volume, and occupies a small mounting space, and the work load of sealing and insulating is reduced so that e cost is reduced and the manufacture efficiency is improved.

The above summary of the invention is not intended to describe each disclosed embodiment or every implementation of the invention. The drawing and detailed description that follows more particularly exemplify illustrative embodiments of the invention.

BRIEF DESCRIPTION OF EACH FIGURE OF DRAWING OF INVENTION

These and other aspects and advantages of the invention should become apparent and more readily appreciated from the following detailed description taken in conjunction with the drawing in which:

FIG. 1 is a partially sectioned perspective view of the DC motor according to an embodiment of the invention;

FIG. 2 is an exploded view of the DC motor according to an embodiment of the invention;

FIG. 3 is a perspective view of the brash holder of the DC motor according to an embodiment of the invention;

FIG. 4 is a plan view of the brush holder shown in FIG. 3;

FIG. 5 is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in a “de-energized” state;

FIG. 6 is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in an “energized” state and the motor rotates in a first direction; and

FIG. 7 is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in an “energized” state and the motor rotates in a second direction opposite to the first direction.

DETAILED SCRIPT ION OF EMBODIMENTS OF INVENTION

Reference is made in detail to embodiments of the invention. The embodiments described herein with reference to the drawing are explanatory and illustrative and used to generally understand the invention. The embodiments should not be construed to limit the invention. The DC motor according to an embodiment of the invention is described below in detail referring to the drawing. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the description.

As shown in FIGS. 1 and 2, the DC motor according to an embodiment of the invention includes a stator 1, a rotator M, a brush holder 3, first and second carbon brushes T1, T2, a current-direction controller 4, and a cover 2. Each of these components is described in greater detail below.

The stator 1 includes a shell 11, a main magnetic pole 12, and an exciting coil X disposed in the shell 11. The rotator M is disposed in the stator 1 to rotate under the action of the magnetic field in the shell 11. The brush holder 3 is mounted at an end of the shell 1 (for example, the right end of the shell 1 as illustrated in FIGS. 1 and 2). The first and second carbon brushes T1. T2 are mounted on the brush holder 3 and in contact with the rotator M, respectively. For example, the first and second carbon brushes T1, T2 are in sliding contact with the commutator of the rotator M. The current-direction controller 4 is disposed on the brush holder 3 and connected with the first and second carbon brushes T1, T2 and first and second ends X1, X2 of the exciting coil X, respectively, to control or change a direction of a current supplied to the exciting coil X. The cover 2 is mounted into an end of the shell 11 to seal the brush holder 3. For example, the cover 2 and the brush holder 3 may be mounted at the end of the shell 11 via a bolt 5. Therefore, as shown in FIG. 1, in an assembled state, the brush holder 3 and the current-direction controller 4 mounted thereon are mounted at an end of the shell 11 and enclosed by the cover 2. As a result, the motor may have a compact structure and occupy a small mounting space. Moreover, because the current-direction controller 4 is disposed inside the cover 2, the current-direction controller 4 and the wires and connection points thereof may not need to be sealed and insulated from outside so that the cost is reduced and the safety and the manufacture efficiency are improved.

In some embodiments of the invention, the DC motor may be a series-excited DC motor. More particularly, as shown in FIGS. 3-7, the current-direction controller 4 includes first and second contactors A1, A2. The first contactor A1 has a pair of normally open contacts K11, K12, a pair of normally closed contacts B11, B12, and a contactor coil KM1. The second contactor A2 has a pair of normally open contacts K21, K22, a pair of normally closed contacts B21, B22, and a contactor coil KM2.

One normally open contact K11 of the first contactor A1 is connected with one normally closed contact B11 thereof and the first end X1 of the exciting coil X via a conducting wire L3 and a conducting wire L8, respectively. One normally open contact K22 of the second contactor A2 is connected with one normally closed contact B22 thereof and the second end X2 of the exciting coil X via a conducting wire L4 and a conducting wire L9, respectively. The other normally closed contact K12 of the first contactor A1 is connected with the other normally open contact K21 of the second contactor A2 via a conducting wire L1. The other normally open contact K21 of the second contactor A2 is also connected with one end of each of the contactor coils KM1, KM2 of the first and second contactors A1, A2, respectively, via a conducting wire L7 and connected with the second carbon brush T2 via a power supply E. The other end of each of the contactor coils KM1, KM2 of the first and second contactors A1, A2 is configured to connect with an end of an external control switch K. Moreover, the one end of each of the contactor coils KM1, KM2 of the first and second contactors A1, A2 (and the other normally open contact K21 of the second contactor A2) is also connected with the negative pole of the power supply E. The other end of the external control switch K is connected with the positive electrode of the power supply E. Therefore, by controlling the external control switch K, the contactor coil KM1 of the first contactor A1 may be energized while the contactor coil KM2 of the second contactor A2 may he de-energized (as shown in FIG. 6). The contactor coil KM1 of the first contactor A1 may he de-energized while the contactor coil KM2 of the second contractor A2 may be energized (as shown in FIG. 7). In addition, the contactor coil KM1 of the first contactor A1 and the contactor coil KM2 of the second contactor A2 may be do-energized simultaneously (as shown in FIG. 5).

The other normally closed contact B12 of the first contactor A1 is connected with the other normally closed contact B21 of the second contactor A2 via a conducting wire L2 and with the first carbon brush T1 via a conducting wire L5.

Therefore, as shown in FIG. 5, when the external control switch K is in its normally “open” position, both the contactor coils KM1 of the first contactor A1 and the contactor coil KM2 of the second contactor A2 are de-energized. The two normally open contacts K11, K12 of the first contactor A1 are disconnected from each other while the two normally closed contacts B11, B12 thereof are connected with each other. In addition, the two normally open contacts K21, K22 of the first contactor A2 are disconnected from each other while the two normally closed contacts B21, B22 thereof are connected with each other so that the DC motor is stopped.

As shown in FIG. 6, when the external control switch K is in its first position (i.e., the “left” position in FIG. 6), the contactor coil KM1 of the first contactor A1 is energized while the contactor coil KM2 of the second contactor A2 is de-energized. The two normally open contacts K11, K12 of the first contactor A1 are connected with each other while the two normally closed contacts B11, B12 thereof are disconnected from each other so that the motor rotates in a first direction.

As shown in FIG. 7, when the external control switch K is in its second position (i.e., the “right” position in Fig. the contactor coil KM2 of the second contactor A2 is energized while the contactor coil KM1 of the first contactor A1 is de-energized. The two normally open contacts K21, K22 of the second contactor A2 are connected with each other while the two normally closed contacts B21, B22 thereof are disconnected from each other so that the motor rotates in a second direction opposite to the first direction.

As shown in FIGS. 3-5, in some embodiments of the invention, the first carbon brush T1 includes two sub-carbon brushes T11, T12 disposed on the brush holder 3 opposite to each other in a radial direction. Similarly, the second carbon brush T2 includes two sub-carbon brushes T21, T22 disposed on the brush holder 3 opposite to each other in the radial direction, in one embodiment, a first line connecting the two sub-carbon brushes T11, T12 of the first carbon brush T1 is substantially perpendicular to a second line connecting the two sub-carbon brushes T21, T22 of the second carbon brush T2. As shown in FIGS. 3 and 4, the two sub-carbon brushes T11, T12 are connected to each other in series via the conducting wire L7, and the two sub-carbon brushes T21, T22 are connected with the shell 11, respectively

As shown in FIGS. 4 and 5-7, the other normally open contact K21 of the second contactor A2 is connected with a negative pole of the power supply F via the conducting wire L7 such that the other normally open contact K12 of the second contactor A1 is connected with the negative pole of the power supply E via the conducting wire L2, the normally open contact K22 of the second contactor A2, and the conducting wire L7, and the second carbon brush 12 is connected with the positive pole of the power supply F via the conducting wire L6.

Therefore, in the series-excited DC motor according to some embodiments of the invention, the current-direction controller 4 includes two contactors, thus reducing the number of the contactors. Moreover, the contacts of the two contactors, the contactor coils, and the wires. are all disposed on the brush holder 3 and enclosed inside the cover 2 such that there are no wires and contactors outside the shell 11. As a result, the motor is compact in structure and small in volume, and the wires and connection points thereof are decreased in number, thus reducing the power consumption. Furthermore, because the current-direction controller 4 is enclosed inside the cover 2, the current-direction controller 4 and the wires and connection points thereof are not necessary to seal and insulate so that the manufacture is much more simple, the cost s reduced, and. the safety is improved.

The operation of the series-excited DC motor according to embodiments of the invention is described below in detail with reference to FIGS. 5-7.

Firstly, as shown in FIG. 5, when the external control switch K is in the “disconnected” position, both the contactor coil KM1 of the first contactor A1 and the contactor coil KM2 of the second contactor A2 are de-energized. The two normally open contacts K11, K12 of the first contactor A1 are disconnected from each other while the two normally closed contacts B11, B12 thereof are connected with each other. Meanwhile, the two normally open contacts K21, K22 of the second contactor A2 are disconnected from each other while the two normally closed contacts B21, B22 thereof are connected with each other. In this way, no current flows through the exciting coil X so that the DC motor is stopped.

When the motor needs to rotate in the first direction, the external control switch K is switched to the first position (i.e., the “left” position as shown in FIG. 6), the contactor coil KM1 of the first contactor A1 is energized, and the two normally open contacts K11, K12 thereof are connected with each other while the two normally closed contacts B11, B12 thereof are disconnected from each other. Meanwhile, the contactor coil KM2 of the second contactor A2 is de-energized, and the two normally open contacts K21, K22 thereof are disconnected from each other while the two normally closed contacts B21, B22 thereof are connected with each other. In this way, the current flows from X2 to X1 in the exciting coil X so that the motor rotates in a first direction (for example, the forward direction), as shown in FIG. 6.

When the motor needs to rotate in a second direction (for example, the reverse direction) opposite to the first direction, the external control switch K is switched to the second position (i.e., the “right” position in FIG. 7),, the contactor coil KM1 of the first contactor A1 is de-energized, and the two normally open contacts K11, K12 thereof are disconnected from each other while the two normally closed contacts B11, B12 thereof are connected with each other. Meanwhile, the contactor coil KM2 of the second contactor A2 is energized, and the two normally open contacts K21, K22 thereof are connected with each other while the two normally closed contacts B21, B22 thereof are disconnected from each other. In this way, the current flows from X1 to X2 in the exciting coil X so that the motor rotates in the second direction, as shown in FIG. 7.

Thus, with the DC motor according to embodiments of the invention, the current-direction controller 4 is mounted onto the brush holder 3 and enclosed by the cover 2 such that the motor is small. in volume and compact in structure, the number of the wires and connection points of the current-direction controller 4 is decreased, and the current-direction controller 4 and the wires and connection points thereof are not necessary to seal and insulate from outside. Therefore, the power consumption and the cost are reduced, and the manufacture efficiency and aesthetics are improved.

Although explanatory embodiments have been shown and described, it should be appreciated by those skilled in the related art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents can he made in the embodiments without departing from spirit and principles of the invention.

Reference throughout this specification to “one embodiment,” “some embodiments,” “an example,” or “some examples” means that a particular feature, structure, material, or characteristic- described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment,” “an example,” or “some examples” in various places throughout this specification are not necessarily referring to the same embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. 

What is claimed is:
 1. A direct-current motor comprising: a stator including a shell, a main magnetic pole, and an exciting coil; a rotator disposed inside the stator; a brush holder disposed at an end of the shell; first and second carbon brushes disposed on the brush holder and contacted with the rotator, respectively; a current-direction controller disposed on the brush holder and connected with the first and second carbon brushes and first and second ends of the exciting coil, respectively, to control a direction of a current supplied to the exciting coil; and a cover disposed at the end of the shell to enclose the brush holder.
 2. The direct-current motor as set forth in claim 1, wherein the motor is a “series excited” motor such that the motor defines a series arrangement of an armature and exciter windings.
 3. The direct-current motor as set forth in claim 2, wherein the current-direction controller includes first and second contactors each of which has a pair of normally open contacts, a pair of normally closed contacts, and a contactor coil, when the contactor coil of the first contactor is energized and the contactor coil of the second contactor is de-energized, the pair of normally open contacts of the first contactor close, the pair of normally dosed contacts thereof open, and the motor rotates in a first direction; and when the contactor coil of the second contactor is energized and the contactor coil of the first contactor is de-energized, the pair of normally open contacts of the second contactor close, the pair of normally closed contacts thereof open, and the motor rotates in a second direction substantially opposite to the first direction.
 4. The direct-current motor as set forth in claim 3, wherein one normally open contact of the first contactor is connected with one normally closed contact thereof and the first end of the exciting coil, respectively, and one normally open contact of the second contactor is connected with one normally closed contact thereof and the second end of the exciting, coil, respectively, and the other normally closed contact of the first contactor is connected with the first carbon brush and the other normally closed contact of the second contactor, respectively, and the other normally open contact of the second contactor is connected with the second carbon brush, the other normally open contact of the first contactor, and an end of the contactor coil of each of the first and second contactors, respectively.
 5. The direct-current motor as set forth in claim 4, wherein each of the first and second carbon brushes includes two sub-carbon brushes, the two sub-carbon brushes of the first carbon brush are disposed substantially opposite to each other in a substantially radial direction on the brush holder, and the two sub-carbon brushes of the second carbon brush are disposed substantially opposite to each other in the radial direction on the brush holder.
 6. The direct-current motor as set forth in claim 4, wherein each of the other ends of the contactor coils of the first and second contactors is adapted to connect with an external control switch. 